Non-Hermitian boost deformation

TL;DR

This paper introduces an imaginary boost deformation method to extend non-Hermitian topological phenomena, such as spectral winding and skin effects, to a variety of integrable models, revealing new non-Hermitian behaviors.

Contribution

It generalizes the concept of non-Hermitian topological effects via imaginary boost deformation across multiple integrable models, including free fermions and spin chains.

Findings

Complex spectral winding observed in free fermion models.

Non-Hermitian skin effect identified in open boundary conditions.

Interaction effects demonstrated in the XXZ model spectrum.

Abstract

The Hatano-Nelson model is one of the most prototypical non-Hermitian models that exhibit the intrinsic non-Hermitian topological phases and the concomitant skin effect. These phenomena unique to non-Hermitian topological systems originate from the Galilean transformation. Here, we extend such an idea to a broader range of systems based on an imaginary boost deformation and identify the corresponding energy-twisted boundary conditions. This imaginary boost deformation complexifies spectral parameters of integrable models and can be implemented by the coordinate Bethe ansatz. We apply the imaginary boost deformation to several typical integrable models, including free fermions, the Calogero-Sutherland model, and the XXZ model. We find the complex-spectral winding in free fermion models under the periodic boundary conditions and the non-Hermitian skin effect under the open boundary conditions. The interaction effect is also shown in the two-particle spectrum of the XXZ model.